The present invention relates to a device for cleaning a gumming applicator.
The invention finds application advantageously in association with mechanisms by which adhesive substances are applied to sheet materials as used in manufacturing and packaging machines for the tobacco industry, the art field to which explicit reference is made in the following specification albeit with no limitation in scope implied.
It is the practice when using machines of the type in question for sheet materials to be gummed by relative applicator mechanisms typically of roller or double disc design.
With a roller type gumming applicator, the adhesive substance is fed directly onto the outer surface of revolution presented by the roller; the surface can be completely smooth so that the adhesive substance is distributed continuously, or indented, affording a plurality of cells by which the adhesive is taken up and distributed in dabs.
Generally speaking, a roller type applicator picks up the adhesive substance directly from a tank in which the gumming roller itself is partly immersed, or alternatively the roller can be supplied with the adhesive substance by a feed device delimited on one side by a substantially cylindrical surface directed toward the surface of revolution of the gumming roller.
In the case of the double disc type applicator, this appears substantially as a pair of coaxially disposed discs identical in diameter, driven in rotation as one and combining to create a central cavity connected externally with the surrounding space by way of delivery slits formed between the discs, and internally with a tank containing the adhesive substance, which is fed under pressure to the central cavity.
One of the main drawbacks experienced with all gumming applicators of the types summarized above is that the adhesive substance used for gumming the sheet material tends to collect on the applicator, generating unwanted accumulations especially at the point of distribution and consequently jeopardizing a correct application of the selfsame substance on the sheet material. Moreover, adhesive substances of the type in question are quick-drying, so that any pause during the operating cycle of the machine with which the gumming applicator is associated, however short, can produce additional accumulations and encrustations which then need to be removed.
Conventionally, roller type gumming applicators are also equipped with a doctor blade positioned at a point preceding the gumming area in the direction of rotation of the roller and riding substantially in contact with the surface of revolution, of which the function, in the case of a completely smooth roller, is to spread the adhesive substance evenly along the length of the revolving surface.
More precisely, in the event that the gumming applicator consists in a roller indented with a plurality of cells destined to receive the adhesive substance, the doctor blade serves both to direct the adhesive into the cells and also to remove the excess adhesive from the inactive surface of the roller not occupied by the cells.
It will be clear however that in performing its principal function as a flow control element, the doctor blade cannot ensure an effective cleaning action either when associated with a roller having a completely smooth face or, in particular, when associated with a roller having an indented face. It follows therefore that the adhesive substance tends to accumulate during each successive gumming cycle, whether on a smooth surface or in the cells of an indented surface, generating residues which impact negatively on the operation of the gumming applicator and must be removed, so that frequent stoppages for cleaning are required.
The problem in question is most noticeable in the case of a double disc type gumming applicator. Indeed with this particular design of applicator it is the discs themselves that control the flow of the adhesive substance and a doctor blade would be incorporated solely in order to perform a cleaning function, which in any event would be ineffective as there is no way that the edge of the blade could wipe the slits in the gumming applicator from which the adhesive substance emerges.
A further drawback deriving from the use of doctor blades as cleaning elements is that residues of the adhesive substance tend inevitably to build up on the blade itself in the course of its inter-action with the gumming applicator. Consequently, frequent interruptions are dictated similarly by the need to remove these accumulations from the surface of the doctor blade.
The object of the invention is to provide a device for cleaning any type of gumming applicator, such as will remove residues of adhesive substances in an effective manner while remaining free of the drawbacks described above.
The stated object is realized in a device according to the present invention for cleaning a gumming applicator, which comprises a source of pressurized fluid and at least one nozzle connected to the source, producing at least one jet of pressurized fluid by which a gumming applicator is invested when in operation in such a way as to remove residues of an adhesive substance from the selfsame gumming applicator.